The present invention relates to a process for gasification of solid carbonaceous material, wherein the solid carbonaceous material is gasified in a gasification reactor furnace with a molten iron bath. Particularly, the present invention relates to a process for operating the gasification reactor furnace which enables the forming of an adhered mass due to splash on the upper part of a furnace, a hood, or a lance to be prevented, and to stabilize the furnace operation and provide a long-lasting operation.
Generally speaking, a so-called coal gasification process using a gasification furnace with a molten iron bath is a process wherein the heat necessary for the gasification is supplied from the molten iron. Among known processes for gasifying solid carbonaceous material, e.g., coal, coke or the like there are disclosed a series of processes in laid-open Japanese patent applications JA-OS 52-41604, 52-41605 and 52-41606. The essential nature of those processes consist of introducing coal into a furnace either by dropping coal onto a bath surface or by introducing coal by the aid of a carrier gas into the molten iron bath through an opening mounted below the bath level, and blowing oxygen and/or steam into the furnace through different means and to different portions in the furnace from the manner and portion by and to which the coal is introduced. Due to such features the coal utilization efficiency at gasification is low and other drawbacks are inescapable as follows:
(I) As, if the coal is dropped on the molten iron, the coal is caught by the floating slag on the bath surface then a part thereof being dissolved into the molten iron by agitation, the loss of coal by splashing away or by floating with the slag without being gasified will increase, the coal utilization efficiency will be as low as not more than 80%, CO.sub.2 content in the resultant gas will not be able to be depressed below 5 to 6%, resulting in no effective gasification.
(II) Sulfur in the floating coal will directly react with oxygen to produce SO.sub.x and thus the expected advantage of the gasification of this type that no sulphur would be contained in the produced gas will be lost.
(III) Since the portion of coal introduction and that of blowing an oxygen jet are different and apart from each other, a hot spot or so-called fire point with a super-high temperature will be formed, e.g., on the surface of the molten iron bath if oxygen is top-blown, loss of the molten iron due to its evaporation will be large, a large amount of combustible metal iron containing micro carbon particles will be contained in the produced gas resulting in danger in dust treatment, and the furnace operation would become difficult due to the iron loss.
DE-OS 2443740 discloses a process also falling within the same essential nature as the abovementioned JA-OS, therefore being inescapable from abovementioned disadvantages.
A known process disclosed in JA-OS 55-89395 applied by the assignee of the present application to a considerable extent eliminated such disadvantages in the prior art aforementioned and the utilization efficiency of C of the solid carbonaceous material was improved. According to this JA-OS, oxygen is top-blown through a non-submerged lance onto a molten iron bath surface forming a hot spot or so-called firing point with a high temperature toward which a solid carbonaceous powder is pneumatically top-blown through a non-submerged lance by the aid of a carrier gas. Thereby, the amount of the solid carbonaceous material caught by the floating slag on the iron bath was reduced. In a furnace of a type usually similar to a converter in which a molten iron bath of 1300.degree.-1500.degree. C. is stored, the coal (powdered coal) and a gasifying agent are top-blown through the non-submerged lance toward the molten iron with the coal thereby being gasified. This process using the converter type furnace facilitates the feeding of the coal and gasifying agent into the furnace, and is capable of gasifying any kind of coal advantageous. However, the molten iron will be splashed from the bath during the operation due to the jet of the gasifying agent resulting in the formation of an adhered mass on the upper part of a furnace, or a hood or a surface of the lance (on water cooling pipe) on its rapid cooling, which would raise difficulties in the operation. Once an amount of the adhered mass has been formed, it will consistently grow until a furnace throat and hood will be likely to be blocked, whereon the pressure control in the furnace is strongly inhibited finally leading to an inoperable condition.
Therefore, according to that process it was difficult to maintain a long-lasting operation particularly on using the converter type furnace, also it was necessary to break or stop the operation in order to remove the adhered mass resulting in non-stable supply of the produced gas, which is drawn to drawbacks of that process.
Slag floating on the molten iron bath level forms from ash in the coal or blown flux will increase. In the prior art, mixing effect of the molten iron bath due to the jet of the gasifying agent will be diminished if the slag layer gets thick. Then the coal utilization efficiency will be depressed as the gasifying agent attains less contact with the molten iron bath resulting in less coal diffusion therein. Therefore it was difficult in the prior art to attain a high coal utilization efficiency without causing to form the adhered mass.